Tesco and three other retailers are investigating how beef burgers on sale in Britain and Ireland became contaminated with horse meat.

Tim Smith, Tesco’s group technical director, apologised for the “distress” the contamination may have caused customers and pledged to uncover how it happened.

“Our investigation will get to the bottom of who is responsible, how it happened and how long it has been going on,” Smith told BBC Radio 4’s Today programme. Answering those questions was vital to prevent the contamination happening again, he added.

‘Illegality or gross negligence’

“There are only two ways it could have happened – illegality or gross negligence,” said Smith. All affected products had been withdrawn from sale.

The contamination came to light after Irish food safety watchdog the Food Safety Authority of Ireland (FSAI) analysed beef burgers stocked in stores in the UK and Ireland. Of 27 burgers analysed, 10 contained traces of horse DNA and three contained pig DNA.

In one sample sold by Tesco, horsemeat accounted for 29% of the total meat content.

Horse DNA was found in the retailer's Everyday Value beef burgers and its frozen quarter pounders.

The FSAI said the contaminated meat was supplied by two processing plants in Ireland and one in Yorkshire. The plants were Liffey Meats and Silvercrest Foods in Ireland and the Dalepak plant at Hambleton in Yorkshire.

‘Frozen burgers – the cheapest you can buy’

Irish agricultural minister Simon Coveney said: “A survey was carried out at the end of November on frozen burgers – the cheapest you can buy in the supermarkets – and the results were passed to me last night [January 15]. One of the tests of 27 showed there was quite a significant horse meat content. 29% of the meat content was horse meat, which obviously I was concerned about.”

Coveney said he had sent Irish government vets into the Irish meat plant concerned to interview management in a bid to discover the origin of the horse meat. “The factory concerned does not slaughter horses and does not import horse meat,” he said.

“It imports certain product – mostly from outside of the state to add to the beef it uses in its beef burgers.”

Coveney stressed the contamination posed no threat to human health.

Contaminated burgers have also been withdrawn from sale in Iceland, Lidl, Aldi and Dunnes Stores.

Aldi said it had removed the affected product from its stores and was investigating the matter.

European third party suppliers

Silvercrest Foods and Dalepak Foods told BBC News they had never bought or sold horse meat. Both added that they had launched an investigation into two continental European third-party suppliers.

Liffey Meats told its customers in a letter today (January 16): “Liffey Meats has never produced, purchased or traded in any equine products.”

The firm said it imported some raw ingredients as part of its manufacturing process for certain products.

It added that the horse DNA identified by the FSAI were supplied by an EU-approved plant and were certified as being from bovine sources only.

“We now believe that such imported raw ingredients were the ultimate source of the DNA traces found in some of our products,” it said.

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